The present invention relates to cleansing compositions. In particular it relates to mild personal cleansing compositions which display improved rinse feel in combination with good skin feel attributes, and foaming properties which are suitable for simultaneously cleansing and conditioning the skin and/or the hair and which may be used, for example, in the form of foam bath preparations, shower products, skin cleansers, hand, face and body cleansers, shampoos, etc.
Mild cosmetic compositions must satisfy a number of criteria including cleansing power, foaming properties and mildness/low irritancy/good feel with respect to the skin, hair and the ocular mucosae. Skin is made up of several layers of cells which coat and protect the underlying tissue. The keratin and collagen fibrous proteins that form the skeleton of its structure. The outermost of these layers is referred to as the stratum corneum. Hair similarly has a protective outer coating enclosing the hair fibre which is called the cuticle. Anionic surfactants can penetrate the stratum corneum membrane and the cuticle and, by delipidization destroy membrane integrity and loss of barrier and water retention functions. This interference with skin and hair protective membranes can lead to a rough skin feel and eye irritation and may eventually permit the surfactant to trigger immune response creating irritation.
Ideal cosmetic cleansers should cleanse the skin or hair gently, without defatting and/or drying the hair and skin and without irritating the ocular mucosae or leaving skin taut after frequent use. Most lathering soaps, shower and bath products, shampoos and bars fail in this respect.
Certain synthetic surfactants are known to be mild. However, a major drawback of some mild synthetic surfactant systems when formulated for shampooing or personal cleansing is that they have what can be described as a xe2x80x9cslippyxe2x80x9d or xe2x80x9cnon-draggyxe2x80x9d rinse feel which is not liked by some consumers. The use of certain surfactants such as potassium laurate, on the other hand, can yield a xe2x80x9cdraggyxe2x80x9d rinse feel but at the expense of clinical skin mildness. These two facts make the selection of suitable surfactants in the rinse feel and mildness benefit formulation process a delicate balancing act.
Thus a need exists for personal cleansing compositions which deliver a xe2x80x9cdraggyxe2x80x9d rinse feel while at the same time having excellent skin mildness, in addition to excellent product characteristics such as lather, cleansing, stability, thickening, rheology and in-use skin feel attributes.
Certain polyalphaolefin oils are known for use in personal cleansing compositions for the skin and hair. References to the use of such oils in personal cleansing formulations are to be found in WO 97/09031, U.S. Pat. No. 5,441,730, WO 94/27574, EP-A-0692244, WO 96/32092 and WO96106596. Hydrophobically modified silicones oils are also known for use in personal cleansing compositions and are disclosed for example in JP 05-310540.
Surprisingly, it has now been found that personal cleansing compositions having a xe2x80x9cdraggyxe2x80x9d rinse feel at the same time as having excellent mildness characteristics are provided by the combination of certain water-insoluble oils, such as certain polyalphaolefin oils, in combination with a mild, water-soluble surfactant system.
Whilst not wishing to be bound by theory, the xe2x80x9cdraggyxe2x80x9d rinse feel is considered to be associated with an increase in wet skin friction. An important mechanism for action of such oils is considered to be their ability to deposit and change the surface energy of the skin, i.e. making the skin surface more hydrophobic. During rinsing, the water film is considered to be the lubricant for the skin, and as surface hydrophobicity increases so the water film is destabilised and the surface de-wetted. As a result the water film is at first thinned and then displaced, allowing some direct contact between the surfaces. Both changes increase friction and produce xe2x80x9cdraggy rinsingxe2x80x9d.
According to the present invention there is provided a rinse-off liquid personal cleansing composition comprising water, from about 1% to about 60% by weight of a water-soluble surfactant and a water-insoluble oil.
The compositions of the present invention provide an improvement in rinse feel while at the same time being exceptionally mild to the skin.
All concentrations and ratios herein are by weight of the cleansing composition, unless otherwise specified. Surfactant chain lengths are also on a weight average chain length basis, unless otherwise specified.